Method for the production of cheese solids

ABSTRACT

In a process for the preparation of a cheese solid and a treatment of the whey solution by a semipermeable membrane, the improvement which comprises: employing, to wash the curd product of the cheese solid, a low BOD effluent fraction derived from a reverse osmosis high-pressure membrane stage used to treat the whey solution; and recycling the wash effluent to the whey solution to be treated, thereby improving the total management of water in the cheese manufacturing process and avoiding waterpollution problems.

United States Patent 1 Timmins et al.

[ 51 Jan. 2, 1973 [54] METHOD FOR THE PRODUCTION OF CHEESE SOLIDS [75]Inventors: Robert S. Timmins, Concord; Bernard S. Horton, Cambridge;Robert L. Goldsmith, Watertown, all of Mass.

[73] Assignee: Abcor, Inc., Cambridge, Mass.

[22] Filed: Aug. 11, 1971 [21] Appl. No.: 170,844

RO PERMEATE OTHER PUBLICATIONS Horton, B. S. Prevents Whey PollutionRecovers Profitable By-Products, Food Engineering, July 1970, pp. 81-83.

Primary Examiner-Hugh R. Chamblee Attorney-Richard P. Crowley [5 7]ABSTRACT In a process for the preparation of a cheese solid and atreatment of the whey solution by a semipermeable membrane, theimprovement which comprises: employing, to wash the curd product of thecheese solid, a low BOD effluent fraction derived from a reverse osmosishigh-pressure membrane stage used to treat the whey solution; andrecycling the wash effluent to the whey solution to be treated, therebyimproving the total management of water in the cheese manufacturingprocess and avoiding water-pollution problems.

11 Claims, 1 Drawing Figure SKIM MILK TO RINSE FORMATION RINSE RINSECHEESE CURB FIRST CURB SECOND CURB THIRD CHEESE RINSE SOLIDS T R0PERMEATE- I FOR REUSE THIRD RINSINGS FQEVERSE WHEY DILUTE E OshoslsSOLUTION WHEY SOLUTION SECOND SECTION -r UF ULTRAFILTRATION PERMEATE -FsEcT|E5N-\ OSMO$|$ SECTION LACTOSE FRACTION LACTOSE LACTOSE SEPARATIONOR RECOVERY up PROTEIN CONCENTRATE FR/anion SPRAY DRYING PROTEINPRODUCTION OF CHEESE SOLIDS BACKGROUND OF THE INVENTION Whey solutionsderived from the manufacture of cheese solids typically have a highbiological oxygen demand, and, therefore, when discharged intowaterways, have created pollution problems. A number of techniques havebeen proposed for handling whey solutions, including the employment ofboth ultrafiltration and processes. For example, the protein fraction ofwhey solutions have been recovered and concentrated employingultrafiltration membranes designed to retain, for example, over 98percent of the alpha lactalbumin and other high molecular weight solublemilk proteins in the whey solution at low pressures of, typically, to100 psi. In the ultrafiltration membrane process, there is, typically,no retention of lactose, salts, vitamins and low molecular weightnitrogen compounds, such as urea and free amino acids.

Reverse osmosis processes and techniques have been employed toconcentrate lactose or whole whey. Reverse osmosis techniques can beused to concentrate either the permeate from the ultrafiltration stageor whole whey directly. In both cases, lactose is retained andconcentrated along with other low molecular weight ingredients. Typicalpressures employed in reverse osmosis techniques would range from about500 to 1,500 psi. The permeate from a reverse osmosis concentration oflactose or whole whey provides for a lactose fraction and a low; forexample, under 1,000 ppm, BOD content effluent fraction of the permeate.Often the BOD of the effluent from the reverse osmosis stage is lowenough so that the effluent fraction may be discharged directly into thewaterways. Typically, the semipermeable membranes employed comprise acellulose ester, such as cellulose acetate, cast on the inside of asupport tube, such as a porous polyolefin, for ultrafiltrationtechniques, or a resin-hardened, braided glass fiber in reverse osmosistechniques.

In a particularly useful and commercial process, there has beendeveloped a two-step treatment of whey solution combining a first stepof ultrafiltration, followed by a second step of reverse osmosis, whichtwostep process offers a number of significant advantages. Such two-steptreatment of whey solutions is described more particularly in an articleentitled Prevents Whey Pollution Recovers Profitable By-Products byBernard S. Horton, Food Engineering, July 1970, which article is herebyincorporated by reference in its entirety. In the two-step process, awhey solution is converted into a protein fraction, lactose fraction anda water effluent fraction with drastically reduced biological oxygendemand (BOD). The first step uses ultrafiltration to produce a fluidprotein concentrate with up to about percent protein and a permeatecontaining most of the lactose salt and other low molecular weightmaterials; that is, materials typically having a molecular weight ofless than 1,000; for example, 50 to 370. In the second step, thepermeate from the ultrafiltration stage is subject to reverse osmosis toyield a concentrated lactose fraction with up to about 20 to percentlactose and a low BOD permeate process effluent fraction which may bedischarged from the plant or reused.

METHOD FOR THE reverse osmosis semipermeable membrane- Whey is theby-product of two groups of cheese manufacturing processes, one of whichproduces a sweet whey and the other, which includes cottage, cream, potand farmers-type cheese, produces an acid whey. In the production ofcottage or colby cheese or similar cheeses, the cheese curd is oftensubject to a number of water rinses to remove lactose and other productsin the curd. For example, a cottage cheese curd may be subject to threeseparate rinse stages. The wash water from such rinses often has anunacceptable BOD demand, and contributes to water-pollution problems.

SUMMARY OF THE INVENTION Our invention concerns a process which improvesthe management of water in a total cheese-manufacturing process, and,further, which reduces the difficulties associated with water pollutiondue to high BOD waste effluent streams from a whey solution. Our processrelates to the efficient and economical utilization of effluent waterderived from a semipermeable membrane process and the employment of suchwater to wash or rinse cheese curd and the recycling of such water intothe semipermeable membrane process after such use, thereby closing theloop in a pollution cycle where a cheese solid is prepared, and thewaste whey solution treated by membrane techniques.

In particular, our invention is directed to the preparation of cottagecheese or colby cheese solids and the treatment of the whey solutionderived therefrom in a reverse osmosis or a two-step ultrafiltration andreverse osmosis process, wherein low BOD effluent derived from thereverse osmosis step is employed to wash or rinse the curd product inthe first wash stage and the wash effluent then added to the wheysolution for recycling.

More particularly, our invention permits a low BOD effluent stream froma reverse osmosis semipermeable membrane step to be employed in a numberof wash or rinse stages and with a portion of the wash effluent recycledto the whey solution, and in the later stages, a portion thereof,together with other rinse water, to be subjected to a separate reverseosmosis treatment by the removal of BOD material and to provide a lowBOD effluent stream suitable for reuse within the plant.

Our invention and process will be described in detail for the purposesof illustration only in connection with the manufacture of a cottagecheese solid. However, it is recognized that our invention may beutilized in any cheese-manufacturing or similar operation which requiresthe curd product to employ low BOD water or which incorporates a rinseor wash stage rather than merely a pressing of the curds. In addition,our process will be described in connection with the preferredembodiment of manufacturing a cottage cheese solid in conjunction withthe treatment of the whey solutionby a two-step ultrafiltration andreverse osmosis process; however, it is recognized that where desired,the whey solution may be treated solely with one or more reverse osmosisstages for the concentration of the protein and lactose fractions, and,accordingly, our process may be employed also in such operation.

DRAWINGS FIG. 1 is a schematic representation of our process employed inthe manufacture of a cottage cheese solid from skim milk with thetreatment of the whey solution by a two-step ultrafiltration-reverseosmosis process.

DESCRIPTION OF THE EMBODIMENTS Skim milk is employed to form a cheesecurd in a typical conventional fashion, producing a solid-curd productand a whey solution. The whey solution is directed for concentration ofthe protein fraction into an ultrafiltration section; for example, in anultrafiltration section which is composed of cellulose acetate formed ina thin film directly on the inside of a plurality of porous polyolefinsupport tubes to provide a seamless membrane tube. The membrane isdesigned to provide over a 98 percent retention of an alpha lactylbuminand other high molecular weight soluble milk proteins. Theultrafiltration is operated at a pressure of 20 to 50 psi at atemperature of about 100 to 140F. The concentrate of the ultrafiltrationsection comprises a protein fraction which may then be dried byevaporation, such as by a spray-drying technique to produce a solidprotein fraction having unique lactose-free properties. The permeatefrom the ultrafiltration section is introduced into a reverse osmosissection operated at a pressure typically of greater than 400 psi; forexample, 600 to 1,000 psi, at a temperature of about 70 to 100F. Thereverse osmosis section may be comprised of a plurality of high-pressuretubes; that is, cellulose acetate membranes cast directly inside anepoxy-resinreinforced braided glass fiber tube. The membranes aretailored to provide a retention of the lactose nonprotein nitrogen acidshaving a molecular weight of typically over 50 or 100. The concentratefrom the reverse osmosis section comprises a lactose fraction which maybe subsequently treated to remove the individual components of thefraction and the lactose present crystallized and rewashed to a highgrade for use or the fraction recovered by drying without furtherseparation. The permeate produced in the reverse osmosis sectioncomprises a very low BOD; for example, less than 2,5 ppm BOD, such asless than 1,000 ppm, and very minor amounts of residual organic lacticacid and other products which may have been passed through the reverseosmosis membrane.

After formation of the cheese curd, typically, cottage cheese curd issubject to a series of rinses as washings illustrated as a first rinse,second rise and third rinse stages, although it is recognized that moreor less stages may be employed as, for example, in the washing of colbycheese wherein typically only one or at the most two rinse stages areemployed. The reverse osmosis low BOD permeate is recycled from thereverse osmosis section to the first rinse stage and employed to rinsethe curd. Typically, such a reverse osmosis permeate stream would have acomposition of about 3 percent or less solids. The effluent from thisfirst rinse stage is then added to the whey solution being introducedinto the first stage ultrafiltration section. The RO permeate is alsoemployed in a second rinse stage; however, due to the very low amount ofsolids in this stage, rather than adding said wash effluents from thesecond rinse stage back into the whey solution which may be done, if

desired, in the preferred embodiment, the second rinse stage is merelydiscarded or otherwise treated as will be hereinafter explained. In thethird rinse stage, as illustrated, regular wash water may be employed.Where desired, the wash effluents from the second or third or subsequentrinse stages may then be subject to a separate reverse osmosis step orother treatment in order to provide a very low BOD water effluent streamwhich then may be employed within the plant; for example, as boilerwater, additional rinsing, or other plant use, or if desired, dischargedwithout significant waterpollution problems. Our process as describedpermits a very efficient and economical combination of a reverse osmosistreatment of a whey solution with the preparation of a solid cheese,while minimizing water-pollution problems and maximizing total watermanagement within the cheese-manufacturing plant.

Our process has been illustrated in a single ultrafiltration and reverseosmosis section; however, it is recognized that where desired, theultrafiltration and reverse osmosis stages may comprise a series ofseparate and distinct stages employing different membranes, pressures,temperatures or other process conditions, or the same processconditions. Further, our process has been described for the purpose ofillustration only employing of a rinse stages; however, the number ofrinse stages may vary and be combined with other manufacturingoperations, such as pressing steps.

Having thus described in our invention, what we claim is: y

1. In a process for the preparation of a cheese solid, which processcomprises: the formation of a curd product and a whey solution, therinsing of the curd product and the treatment of the whey solution by areverse osmosis semipermeable membrane process to provide a concentratedwhole whey or partially demineralized whole whey product and a low BODeffluent fraction of permeate, the improvement which comprises:

employing the low BOD effluent fraction from the reverse osmosis processto wash the curd product, and, thereafter, to add at least a portion ofthe wash effluent from such rinse stage to the whey solution prior tointroduction into the reverse osmosis process.

2. The process of claim 1 wherein the cheese solid is a cottage'or colbycheese.

3. The process of claim 1 which includes washing the cheese curd aplurality of times in successive wash stages.

4. The process of claim 1 which includes employing the low BOD wasteeffluent fraction in a first and a successive second wash stage.

5. The process of claim 3 which includes adding the low BOD effluentfraction from the first wash stage to the whey solution to be separated.

6. The process of claim 3 which includes employing the washings from thesecond and subsequent wash stages as a feed stream to a reverse osmosisstage to provide a low BOD efiluent fraction.

7. The process of claim 1 wherein the low BOD effluent fraction has aBOD content of 2,500 ppm or less.

8. In a process for preparing a cheese solid, which process comprises:forming from a milk product a cheese curd and an aqueous whey solution,the whey solution containing a protein fraction and a lactose fraction;washing the cheese curd so formed with water; separating the proteinfraction from the lactose fraction by employing a low-pressureultrafiltration semipermeable membrane; separating the lactose permeatefraction so obtained by a high-pressure reverse osmosis semipermeablestage into a lactose fraction and low BOD effluent fraction; andrecovering the cheese solid after washing, the improvement whichcomprises;

a. washing the cheese curd with the low BOD effluent fraction from thereverse osmosis stage; and

b. adding the effluent fraction after washing to the whey solution priorto subjecting the whey solution to the ultrafiltration and reverseosmosis semipermeable stages.

9. The process of claim 8 which includes washing the cheese curd aplurality of times in successive wash stages, and employing the low BODeffluent fraction in the first and second wash stages.

10. The process of claim 9 which includes adding only the wash effluentfrom the first stage to the whey solution to be separated.

11. In the process of preparing a cottage cheese solid, which processcomprises: forming from a milk stream a cheese curd product and a wheysolution; washing the curd product with water in a series of at leasttwo successive wash stages; separating a whey solution containing aprotein fraction or a lactose fraction into a protein fraction bysubjecting the whey solution to a low-pressure ultrafiltrationsemipermeable membrane stage to provide a protein fraction and a lactosefraction; separating the lactose fraction into a concentrated lactosefraction and a lowBOD effluent fraction by employing a reverse osmosishigh-pressure semipermeable membrane stage, and recovering the cottagecheese solids, the improvement which comprises:

a. washing the cheese curd product in at least the first and second washstages with the low BOD aqueous effluent fraction derived from thereverse osmosis stage; and

b. adding the wash effluent from the first wash stage to the wheysolution prior to separating the whey solution in the ultrafiltrationand reverse osmosis stages.

2. The process of claim 1 wherein the cheese solid is a cottage or colbycheese.
 3. The process of claim 1 which includes washing the cheese curda plurality of times in successive wash stages.
 4. The process of claim1 which includes employing the low BOD waste effluent fraction in afirst and a successive second wash stage.
 5. The process of claim 3which includes adding the low BOD effluent fraction from the first washstage to the whey solution to be separated.
 6. The process of claim 3which includes employing the washings from the second and subsequentwash stages as a feed stream to a reverse osmosis stage to provide a lowBOD effluent fraction.
 7. The process of claim 1 wherein the low BODeffluent fraction has a BOD content of 2,500 ppm or less.
 8. In aprocess for preparing a cheese solid, which process comprises: formingfrom a milk product a cheese curd and an aqueous whey solution, the wheysolution containing a protein fraction and a lactose fraction; washingthe cheese curd so formed with water; separating the protein fractionfrom the lactose fraction by employing a low-pressure ultrafiltrationsemipermeable membrane; separating the lactose permeate fraction soobtained by a high-pressure reverse osmosis semipermeable stage into alactose fraction and low BOD effluent fraction; and recovering thecheese solid after washing, the improvement which comprises; a. washingthe cheese curd with the low BOD effluent fraction from the reverseosmosis stage; and b. adding the effluent fraction after washing to thewhey solution prior to subjecting the whey solution to theultrafiltration and reverse osmosis semipermeable stages.
 9. The processof claim 8 which includes washing the cheese curd a plurality of timesin successive wash stages, and employing the low BOD effluent fractionin the first and second wash stages.
 10. The process of claim 9 whichincludes adding only the wash effluent from the first stage to the wheysolution to be separated.
 11. In the process of preparing a cottagecheese solid, which process comprises: forming from a milk stream acheese curd product and a whey solution; washing the curd product withwater in a series of at least two successive wash stages; separating awhey solution containing a protein fraction or a lactose fraction into aprotein fraction by subjecting the whey solution to a low-pressureultrafiltration semipermeable membrane stage to provide a proteinfraction and a lactose fraction; separating the lactose fraction into aconcentrated lactose fraction and a low BOD effluent fraction byemploying a reverse osmosis high-pressurE semipermeable membrane stage,and recovering the cottage cheese solids, the improvement whichcomprises: a. washing the cheese curd product in at least the first andsecond wash stages with the low BOD aqueous effluent fraction derivedfrom the reverse osmosis stage; and b. adding the wash effluent from thefirst wash stage to the whey solution prior to separating the wheysolution in the ultrafiltration and reverse osmosis stages.